Posterior segment diseases, such as age-related macular degeneration, account for >10 million cases of visual impairment and blindness, representing a significant burden on the U.S. healthcare system. We believe that the development of novel methods to deliver controlled-release formulations specifically to diseased tissues in the eye, while sparing non-diseased tissues, can be efficacious, as well as simplifying the dosing regimen, of the treatment of many posterior segment diseases. Micron-sized needles, aka microneedles can be used to deliver drugs into the suprachoroidal space (SCS: a potential space between the choroid and sclera). This drug delivery system can be advantageous in the treatment of many posterior segment diseases because it (i) bypasses ocular barriers without penetrating through the retina, resulting in higher bioavailability; (ii) delivers drugs adjacent to the choroid, resulting in higher concentrations in the chorioretina; and (iii) prevents diffusion of drugs to other regions of the eye, limiting side effects. Because SCS microneedle injections are a relatively new technology, this proposed work will carry out basic studies to determine the pharmacokinetics of particles and fluid carrier injected into the SCS using a microneedle. Specifically, we propose to (1) Identify relevant anatomical barriers that limit the spread of fluid in the SCS; (2) Determine the kinetics of SCS expansion, and the role of this kinetics in the deposition of particles injected in the SCS; and (3) Determine the kinetics an mechanism of SCS collapse, and verify that SCS collapse arrests particle motion. In-depth knowledge on SCS pharmacokinetics will enable the continued development of therapies and strategies to treat posterior segment diseases. The fellowship applicant seeks to become a successful and independent physician scientist specializing in ophthalmology and engineering technologies to combat vision loss. To reach this goal, the applicant will learn to (i) identify clinical needs and evaluate proposed solutions, (ii) plan and execute a research plan, and (iii) develop effective communication and leadership skills. At the start of this award, the applicant will have completed 2 years of medical training at the Emory School of Medicine and 2 years of graduate study in the joint biomedical engineering department of the Georgia Institute of Technology and the Emory School of Medicine.